There is a need for a high strength structure with corrosion resistant internal metal surfaces as, for example, a gate valve installed in a line containing corrosive fluids under high pressure. Such a valve could be made of AISI 4130 steel and have an interior (valve chamber and passages) lined with a 300 Series stainless steel.
Many attempts have been made to provide such structures. U.S. Pat. Nos. 3,349,789 and 2,497,780 each provide valves with liners which must be secured and sealed in the flow passages but no provisions are made to line the valve chambers.
Products have been made by the hot isostatic pressure process by creating a space which is filled with powdered metal and surrounded with a flexible material which can maintain a seal under the forming temperature and pressure. The powdered metal when subjected to the heat and pressure becomes consolidated into the desired shape. The prior art methods have been devoted to forming solid structures or coating the exterior of a structure. Other examples of prior art may be found in U.S. Pat. Nos. 3,631,583, 3,992,202 and 4,142,888, but such prior art does not disclose any method of using the hot isostatic pressing process to form a lining within cavities of a structure such as, for example, a valve body or a blowout preventer body.